watashi wa shuumatsu ni tomodachi to issho ni geemu o shimasu.

topic particle

Breakdown of watashi wa shuumatsu ni tomodachi to issho ni geemu o shimasu.

• 私わたし: I
• を: direct object particle
• 友とも達だち: friend

Questions & Answers about watashi wa shuumatsu ni tomodachi to issho ni geemu o shimasu.

What does は after 私 do here? Is it the subject marker?

は is the topic marker, not exactly the subject marker.

• 私 = I / me
• 私 は = As for me / Speaking about me

So the sentence is literally:
「私 は 週末に友達と一緒にゲームをします。」
→ As for me, on weekends, (I) play games together with (my) friend(s).

The true grammatical subject can be left out (here it’s understood as “I”), but は just marks what the sentence is about. In many simple sentences, topic and subject are the same person/thing, which makes it feel like a “subject marker,” but conceptually they’re different.

You could replace 私 with something else:

• 弟は週末にゲームをします。
  As for my little brother, he plays games on weekends.

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Why is there に after 週末? What does 週末に mean exactly?

The particle に after a time expression marks when something happens.

• 週末 = weekend
• 週末に = on the weekend / at the weekend

So 週末に tells us the time of the action ゲームをします (play games).

In general, you use に with specific points in time:

• ３時に = at 3 o’clock
• 日曜日に = on Sunday
• 誕生日に = on (my) birthday

Some very broad time words often drop に (like 毎日, 明日), but 週末に with に is perfectly natural and common.

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